This invention relates to a system for the heating, ventilating and cooling of a passenger and/or utility space of vehicles. The system is of the type having a heat exchanger connected to a cycle that takes up the heat of an internal-combustion engine for the heating of the vehicle, as well as a condenser and an evaporator which are part of a compression-type air-conditioning unit. During the cooling, the fresh air, after flowing through the condenser and the heat exchanger, is led into the open air or atmosphere, whereas, during the heating or ventilating operation, the fresh air enters the passenger and/or utility space as ingoing air.
A system of this general type, as used in a motor vehicle equipped with a Stirling engine, is known from German Published Unexamined Application (DE-OS) No. 27 12 178, where, for the removal of the occurring large volume of heat, the heating air exchanger is switched on continuously.
However, in the case of conventional internal-combustion engines, the heating of passenger and useful spaces has become increasingly difficult. Because of their continually more effective or efficient operation and because of the decreasing output requirement of the vehicles for reasons of reduction of the rolling or air resistance as well as of mass, the heat to be removed via a cooling cycle becomes progressively less, and therefore less heat is available for the heating cycle. The trend in this direction is also increased by the fact that the progressively more functional motor vehicles are used at continuously lower outside temperatures.
Since the heat requirement is determined mainly by the quantity of heat of the outgoing air flowing with the outgoing air out of the passenger and/or utility space, it was contemplated to add a changeable proportion of circulating air to the heated ingoing air so that the proportion of outside air having a low temperature will decrease. However, this is possible only to a limited extent because otherwise the relative humidity, because of the reduced flow of outgoing air, will increase so much that a visibility-impairing fogging or icing will occur on the cold windows. In addition, it is absolutely necessary for the well-being of the passengers and the driver that a frequent renewal of air takes place by means of a correspondingly high portion of fresh air.
In order to remedy this situation, it has been contemplated to install additional heaters which, however, apart from the additional energy, also require additional space for the housing of the required aggregate and the necessary pipes.
While not requiring an additional heater in vehicles, it is an object of the invention to achieve, in vehicles which have a compressor-type air-conditioning unit in addition to a heat exchanger connected to the cooling cycle of the internal-combustion engine for the heating operation, an improvement of the heat output with the lower expenditures and without restricting the operational capacity of the system in the normal case. This object is achieved according to the invention by utilizing the heat energy of the outgoing air while avoiding the disadvantages of the operation with a high proportion of circulating air.
According to preferred embodiments of the invention, a system for the heating, ventilating and cooling of the initially described type is provided where the evaporator is arranged in the flow of outgoing air of the passenger and/or utility space and this flow, by means of at least one adjusting device, is directed in such a way that, during a cooling operation, it is again led as ingoing air into the passenger and/or utility space, whereas in the case of a heating or ventilating operation, the outgoing air flow will go out into the atmosphere. Further, according to the counter-flow principle, during the cooling operation, the occurring fresh air, after flowing through the condenser and the heat exchanger, will be led into the open air, whereas, in the case of a heating or ventilating operation, the fresh air, as ingoing air, will enter the passenger and/or utility space, and where, moreover, in order to achieve a maximum heating output, the air-conditioning unit can be activated and then the energy content withdrawn from the outgoing air in the evaporator, via the condenser, is directly or indirectly, in order to aid the heating, again discharged in the ingoing air and is led in front of the heat exchanger connected to the heating cycle.
On the basis of U.S. Pat. No. 2,801,827, it is known, by utilizing the cooling cycle of an air-conditioning unit, to let off the heat energy taken up via an evaporator on the side of the condenser and to use it for the heating of the vehicle. However, this heating system is the only source of heat. In addition, the system must have two reversable cooling cycles with a total of three heat exchangers, in which case one heat exchanger operates as a condenser or evaporator.
A high flow rate of air can be obtained according to preferred embodiments of the invention when, in addition to a connectable fan taking in fresh air, another fan is provided that increases the flow of outgoing or circulating air which, in addition to the cooling and drying operation, is also in use during an extensive heating and ventilating operation.
In a preferred embodiment of the invention, during the cooling operation, an amount of fresh air that maintains a certain internal pressure level is led to the intake side of the fan returning circulating air, via a pipe connected to the atmosphere, resulting at the same time in a more comfortable rate of fresh air flow. So that in other types of operation, no outwardly directed air flow can occur through this pipe, a return valve is disposed in the pipe or at its end.
In order to be able to obtain a sufficient heat output also in the case of lower outside temperatures during a normal heating operation without the aid of the air-conditioning unit, it is advantageous according to preferred embodiments to provide a pipe extending from the passenger and/or utility space, preferably from the pressure side in front of the evaporator to the intake side of the fan delivering fresh air, through which circulating air is added, as required.
In a further development of the invention, the adjusting device is constructed as a four-way guide in the form of a flap which, in regard to the drive and space, results in significant advantages.
The engine cooling is aided when, during an extensive cooling operation of the passenger and/or utility space, the heat exchanger is acted upon by an engine coolant.